Police who met the wayward jet said the pilots were "cooperative, apologetic and appreciative."

The airport police report, released Friday, said officers asked flight attendants to keep passengers in their seats while they checked out the cockpit.

The report identified the pilot as Timothy B. Cheney and Cole as the first officer.

"The pilot ... indicated they had become involved in conversation and had not heard radio communications," the report said. "They indicated there had been no involvement from anyone in the cabin."

The report said, "Both volunteered to a preliminary breath test with the result being .000 for both parties."

The lead flight attendant told officers she was unaware there had been an incident aboard, the report said.

The National Transportation Safety Board, which is investigating the incident, is hoping the plane's cockpit voice recorder will either confirm the pilot's account or provide evidence of another possible explanation, including whether the captain and first officer had fallen asleep.

Earlier, the NTSB released a statement that said, "The crew stated they were in a heated discussion over airline policy and they lost situational awareness."

The voice recorder is capable of recording only 30 minutes of audio, federal accident investigators said Friday. The plane was in the air for another 45 minutes after radio contact was restored, meaning that if the recorder was working properly, anything the pilots would have said during the time they were not answering radio calls would have been recorded over.

But a former accident investigator said the voice recorder may still provide valuable information, because the pilots could have discussed the earlier events on the way back to Minneapolis.

The separate flight data recorder also could prove valuable because it would have recorded actions taken by the pilots during the 78 minutes they did not respond to repeated calls from air traffic controllers, the investigator said.

The safety board said Friday that experts were reviewing the solid-state voice recorder. It said the recorder "captured a portion of the flight that is being analyzed" and added there would be no further comment.